Wet sanders are useful in abrading and removing surface defects or smoothing a variety of non-porous or nonhydrophilic surfaces in preparation for finishing with a sealing and/or protecting finish such as paint. Such wet sanders are commonly used following automobile repairs to smooth and prepare the automobile body for refinishing and repainting.
Most wet sanders use electrical or hydraulic power means to move an attached abrasive article, such as an attached strip or circle of wet-or-dry sandpaper, across the surface to be finished. Typical of such powered sanders are the orbital wet sanders, such as those disclosed in U.S. Pat. Nos. 4,523,411 to Freerks, 4,102,084 to Bloomquist, and 4,175,359 to Teague, Jr. While these mechanized devices have their uses, they may be too large to operate in cramped spaces or to provide the very smooth final finish required before painting. Additionally, they tend to be quite expensive and, thus, not a practical alternative for the do-it-yourselfer.
Manual wet sanding can be performed by using a dry sanding block and periodically dipping the sandpaper into water or periodically pouring water onto the surface being worked. Unfortunately this is inconvenient and does not provide sufficient fluid to lubricate the surface continuously and remove the particles abraded away to prevent a build up of the abraded particles on the surface and on the sandpaper.
Another means for manual wet sanding is disclosed in U.S. Pat. No. 4,484,419 to Freerks which provides a hand sander containing a reservoir for liquid which could be wiped onto the working surface through an opening in the sandpaper attached to the bottom of the sander. The water is prevented from flowing onto the surface by a hydrophilic sponge which wipes the water over the surface. This approach has many problems. First, and most importantly, there is no flow of water over the surface to help flush the abraded particles away and provide a continuously changing film of lubricant on the working surface. Second, for a hand sander, the reservoir would be necessarily limited in size and would need to be filled periodically. Third, the sponge which prevents the flow of the water could become worn or clogged with abraded particles, and would thus need to be cleaned and adjusted periodically to make sure it continues to contact the working surface. Further, when the reservoir empties, the sponge would act to remove water from the surface being worked. Finally, special sandpaper would have to be used since it would have to have an opening to permit the sponge to pass through the sandpaper and contact the working surface. Such sandpaper would have a smaller abrasive area than sandpaper without the opening and would, thus, require more frequent changes.
Yet another approach to manual wet sanding was taken in U.S. Pat. No. 4,320,601 to Haney which discloses a manual sanding block which provides for a continuous flow of water to the working surface by flowing water from an external source through an inlet in the sanding block and out through a sharpened outlet which projects beyond one wall and penetrates the attached strip of sandpaper. Unfortunately, this only provides one outlet for water to flow onto the working surface and, by directing water out one side only does not insure that the sandpaper will pass across a fresh film of water with each stroke. This problem is overcome to some extent on a horizontal surface by the movement of the sanding block over the water flowed onto the surface, but would appear to be a significant problem when the sanding block is used on a surface that is vertical or near vertical and the orientation of the outlet is any direction other than "up". Further, because the sandpaper backing may become easier to tear or destroy as it becomes wet, an outlet which penetrates or otherwise affects the integrity of the sandpaper may serve as a source of tears which could render the sandpaper useless and require frequent replacement. Additionally, while a gentle flow of liquid is desirable, a high pressure stream of liquid is not. To prevent messy working conditions and an unnecessary waste of the liquid used, the flow rate of the liquid should be controlled or regulated. The '601 patent does this by including an adjustable valve on the sanding block to control the flow passing through the single outlet. However, valves can leak or become inoperative, and may not provide a proper flow in the hands of an unskilled worker.
Therefore, the need exists for a manually operated wet sander which can use standard strips or rolls of sandpaper, which removably secures the sandpaper in place by a method which does not penetrate or otherwise affect the integrity of the sandpaper, and which provides a controlled flow of water over surfaces ranging from horizontal to near-vertical.